Automated spar assemby tool

ABSTRACT

An automated assembly machine for fabricating large mechanical structures including a floor assembly jig for receiving and holding parts in a desired orientation, a pair of carriages, a first drive mechanism for independently driving the carriages longitudinally, a second drive mechanism for moving the carriages vertically, a tool tray mounted on the carriages, and a plurality of tools, including a drill, a hole diameter measurement probe, a nut runner, and an electromagnetic riveter, mounted on the tool tray for lateral movement toward and away from a workpiece clamp-up position. The tools are positioned at the workpiece clamp-up position by moving one of the carriages longitudinally along the floor assembly jig and raising the other carriage to elevate the tool tray to a desired elevation.

This application is a continuation of prior application Ser. No.07/949,177, filed Sep. 21, 1992, now abandoned.

This invention relates to automated assembly equipment, and moreparticularly to an automated airplane wing spar assembly tool forclamping the parts of the spar in the correct position, and performingvarious machining and fastener installation operations, such as:drilling fastener holes in the assembled parts of the spar, cold workingand reaming the holes and checking for dimensional conformance with thespecification, inserting bolts and threading nuts on the bolts andtorquing the nuts to the proper torque, inserting lock bolts in theholes and installing collars on the lock bolts and swaging the collarson the lock bolts with the proper tension in the lock bolt, andinstalling rivets in holes and upsetting the rivets.

BACKGROUND OF THE INVENTION

Large structural components which are part of larger structures andwhich must be fabricated to close dimensional tolerances are typicallyassembled on hard tooling and fastened together by hand. This entailshigh labor costs and continual calibration and maintenance of thefixturing tooling, which can experience very hard usage in the factory.An example of such a structure is an airplane wing spar, which is astructural component of an airplane wing that couples the upper andlower wing skin and provides stiffness to the wing. Each wing has aforward and a rear spar, each bent to accommodate the sweptconfiguration of the wing. As a consequence, there are four unique sparson each airplane, each of which would normally require its own toolingand associated periodic calibration and maintenance.

The cost of manual assembly of large mechanical structures can beconsiderable, especially when the structure must be built to very closedimensional tolerances. The assembly procedure requires highly skilledlabor and often requires rework when stringent quality requirements,such as exist in the airframe industry are not met by some rivet orother fastener. Moreover, the hand assembled structures require longassembly times which can increase the number of tooling sets requiredwhen high volumn production is needed.

The parts to be assembled to make the structure should be easily loadedonto the assembly machine and be positionable thereon with greataccuracy and speed. It is probably necessary to provide a fineadjustment on the machine to ensure that the parts are located thereonat the exactly correct position, within the required dimensionaltolerances.

An automated assembly machine must perform all of the operationsperformed by the manual process, including all the routine ones such asrivet insertion and threading nuts on bolts. All these processes must beperformed with speed and precision and must be repeatable for thousandsof cycles without fault to avoid the need for time consuming operatorintervention.

Flexibility is a desirable attribute of an automated assembly machine.In the event that one of the machines requires service, it would be avaluable feature if one of the machines could be reconfiguredtemporarily, and quickly, to enable the assembly of the structurenormally made on another machine on that machine, thereby maintainingthe necessary flow of completed structures to the factory.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide an automaticassembly machine for large mechanical structures that can quickly andaccurately position and clamp the parts for the structure on themachine, and then perform the operations on the machine that are neededto fasten the parts together into a unitary structure in which alldimensions are reliably within tolerance.

These and other objects of the invention are attained in a machinehaving a floor assembly jig on which are mounted a multiplicity ofclamps for receiving and holding the parts in a desired orientation withrespect to each other and in a desired position in space, clampedtogether in a workpiece clamp-up position. The jig has supports andguides for supporting and guiding a pair of carriages along the lengthof the machine on opposite sides of the workpiece clamp-up position. Thecarriages are supported and guided on the supports and guides onopposite sides of the workpiece clamp-up position. A drive mechanism foreach carriage independently drives the carriages longitudinally alongsaid guides and supports. A special bearing and jacking arrangementenables the carriages to negotiate a bend in the floor assembly jigwhile maintaining the normality of the tool axis on the carriage withthe plane of the workpiece.

A tray frame is mounted on each of the carriages for vertical movementrelative to the carriage, and a second drive mechanism moves each of thetray frames vertically with respect to the carriage. Each tray frameincludes a clamp nose that can me moved toward and away from theworkpiece to clamp the workpiece between the clamp noses on the two trayframes while processing operations are carried out, such as drilling,riveting, etc. The two drive mechanisms enable the tray frame to bepositioned accurately at any desired position along the surface of theworkpiece for the processing operations.

A tool tray is mounted on a shifting mechanism on the tray frame forlongitudinal movement on the frame relative to the tray frame and theclamp nose. The tool trays carry a plurality of tools, including adrill, a hole diameter measurement probe, a nut runner, and anelectromagnetic riveter. The tools are mounted on slides on the tooltray for lateral movement toward and away from said workpiece clamp-upposition. A motive device is provided for moving each of the toolstoward and away from said workpiece clamp-up position. The tools canthus be positioned at any desired position along the surface of theworkpiece by moving the carriages along the floor assembly jig to thedesired longitudinal position, and raising the tray frame to elevate thetool tray to the desired elevation, and then shifting the tool traylongitudinally along the tray frame to align the tool with the clampnose. The tool can then be slid through the hollow clamp nose to engagethe workpiece. The tool tray can be moved as often as needed to engagethe tools with the workpiece through the clamp nose without disengagingthe clamp nose until all operations at that position are finished.

DESCRIPTION OF THE DRAWINGS

The invention, and its many attendant objects and advantages will becomemore apparent upon reading the description of the preferred embodimentin conjunction with the drawings, wherein:

FIG. 1 is a perspective view of an automated assembly machine inaccordance with this invention;

FIG. 2 is a schematic plan view of a pair of airplane wings, showing theposition of the wing spars therein;

FIG. 3 is a schematic plan view of the machine of FIG. 1, showing thelayout of the FAJ sections for the several spars;

FIG. 4 is an enlarged perspective view of a portion of the FAJ and thecarriage working on a spar held in the FAJ;

FIG. 5 is a cross section of an airplane wing showing a spar andportions of connected wing skins;

FIG. 6 is an end elevation of a clamp pillar supporting a clamp forholding the spar chords and web in position for fabrication into a spar;

FIG. 7 is a side elevation of the structure shown in FIG. 6;

FIG. 8 is a plan view looking down on the structure shown in FIG. 6;

FIG. 9 is an enlarge end elevation of the structure shown in FIG. 6 withsome parts broken away for clarity;

FIG. 10 is an enlarge end elevation of the clamp shown in FIG. 6;

FIG. 11 is an enlarged side elevation of the clamp shown in FIG. 10;

FIG. 12 is an elevation of a clamp and clamp bracket used for loadingparts on the FAJ;

FIG. 13 is a schematic view of the lift door on which the structure ofFIG. 6 is mounted;

FIG. 14 is an end elevation in the direction of the X-axis showing theFAJ and a pair of carriages working on a spar held in the FAJ;

FIG. 15 is a side elevation in the direction of the Z-axis showing aportion of the FAJ and one of the carriages;

FIG. 16 is an elevation of the tray frame, the tray platform, and thetool tray;

FIG. 17 is a cross-sectional elevation in the direction of the X-axis ofa bearing block and an attached jack screw;

FIG. 18 is a cross-sectional elevation along lines 18--18 in FIG. 12;

FIG. 19 is an end elevation of the headstone and rotating nose forclamping the parts while performing manufacturing operations on them;

FIG. 20 is an enlarged cross-sectional elevation of a portion of thestructure shown in FIG. 19, showing the brake for the rotating nose;

FIG. 21 is a plan view of the structure shown in FIG. 19

FIG. 22 is an elevation of the wet side tray platform showing the headstone and the tool tray;

FIG. 23 is a plan view of the dry side tool tray, on opposite side ofthe workpiece from the tray platform shown in FIG. 22;

FIG. 24 is a side elevation of the tool tray shown in FIG. 23;

FIG. 25 is an end elevation of an automatic lubrication tool mounted onthe tool tray in FIG. 22;

FIG. 26 is a side elevation of the lubrication tool shown in FIG. 25;

FIGS. 27 and 28 are end elevations of the lubricant applicator mountedon the lubrication tool of FIG. 25, shown in "off" and "on" positions inFIGS. 27 and 28, respectively;

FIG. 29 is an end elevation of the hole checker mounted on the wet sidetool tray shown in FIG. 22;

FIG. 29A is an enlarged elevation of the probe of the hole checker shownin FIG. 29;

FIG. 30 is an even more greatly enlarged sectional elevation of the holechecker probe shown in FIG. 29;

FIG. 31 is an enlarged elevation of the hole checker shown in FIG. 29;

FIG. 32 is an elevation, partly in section, showing the hole checkermounted on the wet side tool tray in both extended and retractedpositions;

FIG. 33 is a sectional elevation of a fastener feed system for feedingfasteners to the fastener inserters on the dry side tool tray;

FIG. 34 is a plan view of the fasterer feed system shown in FIG. 33;

FIG. 35 is an elevation of a nut feed device mounted on the wet sidetool tray shown in FIG. 22;

FIG. 36 is a side elevation of the nut feed device shown in FIG. 35; and

FIG. 37 is an elevation of the nut runner mounted on the wet side tooltray shown in FIG. 22.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning now to the drawings, wherein like numerals designate identicalor corresponding parts, and more particularly to FIG. 1 thereof, anautomated spar assembly machine is shown for producing wing spars forlarge transport airplanes. Although the invention can be used forproducing many different types of large mechanical structures, the sparassembly machine will be described for purposes of illustration. Forthis purpose, a brief description of airplane wing spars will be usefulto understand the machine.

As shown in FIG. 2, an airplane wing normally has two spars, a frontspar and a rear spar. The spars are not symmetrical about theirhorizontal centerlines, so the right and left wings each have a uniquefront and rear spar. Each spar has a bend 22 approximately one thirdfrom the root end 24, and each spar tapers in height from the root end24 to the outboard end 26. Each spar has a "wet side" and a "dry side"referring to the fact that fuel is carried in the wings and the insidesurfaces (the "wet side") of the spars comprise part of the fuel tanks.

The spar assembly machine of this invention includes a floor assemblyjig 32 (commonly referred to as an FAJ) having one section for eachspar. The four sections of the FAJ 32 are arranged as shown in theschematic of FIG. 3 and are each substantially identical except for theangle of the bend 22 and the position of the clamps, as will bedescribed below. The FAJ 32 includes a series of floor-mounted C-frames34 which carry a top track 36 at their top ends, and a bottom track 38on a floor-mounted base section 40 of the C-frames. A multiplicity ofclamp support pillars 42 are mounted centrally on the bottom track 38and the top track 36, extending vertically toward each other anddefining between them a workpiece clamp-up position. The clamp supportpillars 42 extend in line axially along each section of the FAJ 32 foralmost its full length. A pair of carriage support and guide rails 44and 44' is mounted on the bottom track 38 on both sides of the line ofclamp support pillars 42 and extend parallel to each other the fulllength of the FAJ 32.

A carriage 46, shown in FIGS. 4 and 14, is supported vertically on eachof the rails 44, and is supported laterally at the top of the carriageby one of two top rails 48 secured to the top track 36, one for eachcarriage. Each of the four sections of the FAJ, one for each spar, has apair of carriages 46, but they are so similar that only one pair ofcarriages 46 will be described. The two pairs of carriages for the frontor rear spar can be moved along the track from the right or left handFAJ to both operate on a single spar 20 from opposite ends while partsare being installed on the other hand FAJ if needed.

A typical rear spar is shown in FIG. 5. It includes a web 50 an upperchord 52U, and a lower chord 52L. The upper chord 52U, has a verticalleg 54U and a "horizontal" leg 56; the lower chord 52L has a verticalleg 54L and a "horizontal" leg 56L. As illustrated in FIG. 5, the"horizontal" leg 56 is not exactly horizontal, that is, it makes anangle with the vertical leg that is slightly greater than 90°, becauseof the chord-wise curvature of the wing. On the upper chord 52U, theangle that the horizontal leg 56U makes with the vertical leg 54U isgreater than the corresponding angle on the lower chord 52L because thecurvature of the upper wing skin 58 is greater than that of the lowerwing skin 60. A series of stiffeners 62 are fastened to the dry side ofthe spar 20B, and a series of rib posts 64 are fastened on the wet sideof the spar for attachment of the wing ribs that extend between thefront and rear spars.

As shown in FIGS. 6-11, the clamp support pillars 42 carry clamps 66 forclamping the chords 52 at the correct position to ensure that thevertical dimension of the spar 20 will be correct. The clamps 66 areeach mounted on the distal end of a clamp post 68 which, as best shownin FIG. 7, is connected to a clamp support pillar 42 by a vertical slidehaving a track 70 mounted on the pillar 42 and a pair of spacedfollowers 72 and 72' mounted on the post 68. A set of recirculatinglinear bearings between the track 70 and the followers ensure that thepost will slide smoothly on the pillar 42, and that the post will besupported on the pillar in a precisely vertical orientation.

An air cylinder 74, best shown in FIGS. 6 and 9, is connected betweenthe post 68 and the pillar 42 for vertical support of the post on thepillar. The air cylinder 74 has a piston rod 76 connected at its top endto the post 68, and is connected at the bottom end of the cylinder 74 toa bracket mounted on the pillar 42. The air cylinder 74 is pressurizedto exactly counterbalance the weight of the post 68 and the clamps tomake movement of the post and the clamps easy when the height of theclamps is to be adjusted. The vertical position of the post on thepillar 42 is set by a pin 78 extending through pairs of alignedapertures 80 and 82 in two alignment plates 84 (only one of which isseen in FIG. 9) secured to the post 68 and pillar 42, respectively.

The two different heights provided for the clamps 68 are to enable theright hand spars to be made on the left hand FAJ, and visa-versa.Because of the bend 22 in the spars, it is necessary to make the sparsin an inverted orientation when making them on an opposite hand machine,and since they are not symmetrical about the horizontal centerline, itis necessary to reconfigure the clamps to correspond to the inverteddimensions on the spar. When the FAJ 32 is to be reconfigured to make aspar of the opposite hand, it is merely necessary to pull the pin 78 outof the aligned apertures 80 in the aperture plates 84 and move the poston its slide connection to the pillar 42 to the position at which theapertures 82 are aligned, and reinsert the pin 78 through the alignedapertures 82. The configuration change is fast and easy, and it isextremely accurate. It could also be expanded to enable spars for othermodel airplanes to be made on this FAJ by merely providing otheraperture plates drilled appropriately to position the clamps 66 at thecorrect height for that design of spar.

Once the FAJ 32 is configured to the correct dimensions for the desiredspar, the parts which make up the spar must be loaded on the FAJ. First,the carriages are moved to a parking position at the end of the FAJ 32,and then a web 50 is lifted into position onto a series of temporary webindex support posts 90. The support posts 90 are provided with indexpins that fit into locating holes drilled in the web 50. When the web ispresented correctly to the FAJ 32, the pins on the support posts 90 willfit into the holes in the web 50 and the web will be supported at thecorrect position on the FAJ 32.

The web 50 is loaded onto the FAJ by a parts loading system shown inFIGS. 12 and 13. It includes a series of towers in the form of largebrackets 91 slidably mounted on a series of flip doors 92 hinged atpivot points 93 to the inner edge of a scaffold 94 supported on thefloor at a position spaced far enough-from the FAJ to permit passage ofthe carriage 46 along the FAJ 32. The brackets 91 may be pushed onslides 95 on the flip doors 92 toward and away from the workpiececlamp-up position 67 on the FAJ to carry parts for loading onto the FAJ.The flip doors 92 include a hinged support leg 96 which swings down toengage a stop on the scaffold 94 and support the flip doors 92 in theirhorizontal position. The flip doors 92 provide a bridge from thescaffold 94 to the FAJ 32 for convenient access by workers, and can berotated upward to provide a clear passage for the carriage 46.

In operation, a crane lifts the web 50 onto a set of stops 97 on clamps98 which have clamp arms 99 that close on the web 50 and hold it in theclamps 98. The brackets 91 can be pushed on their slides 95 laterallyfrom a web receiving position over to a web loading position adjacent tothe FAJ 32, at which position the web is correctly positioned to bepushed onto the index pins 89 of the web index support posts 90. Thebrackets 91 are then retracted, and two chords 52U and 52L are loadedonto the stops 97 on the clamps 98 which accurately locate the chords52U and 52L so that they will engage stops on the clamps 66 when theclamp brackets 91 are pushed against the FAJ 32.

When the chords 52 are positioned on the stops on the bracket clamps 98,a sealant is applied to the faying surface of the vertical legs 54U and54L of the chords 52U and 52L that will contact the web, and the solventis allowed to flash off from the sealant. The brackets 91 are then slidup against the FAJ to place the chords against the web and in positionagainst locating surfaces on the clamps 66. The clamp arms 99 on theclamps 98 are released one at a time and a jack screw 100 is turned tolift the chord against a horizontal stop 102 on the clamp to ensure thatthe distance between the outside corners 104U and 104L of each chord,shown in FIG. 5, are the correct distance, since the wing skins 58 and60 will be fastened directly to these chords. As each jack screw bringsthe chord into engagement with the clamp stop 102, the clamp is manuallyactuated to clamp the chord 52 to the clamp 66 at that position. Whenall the jack screws 100 have been adjusted, all the remaining chordclamps are actuated by a central control (to be described below) tosecure the chord rigidly in position on the clamps. Then a series ofweb-to-chord clamps are actuated to clamp the web to the vertical legs54U and 54L of the chords 52U and 52L. Some tack rivets can be installedto prevent any slippage of the web on the chords, and the web indexsupport posts 90 can be removed, and the lift door can be lowered toclear the space adjacent the FAJ for travel of the carriage on that sideof the FAJ. When the chords are being riveted to the web and other highcompression fasteners are being installed, a small amount oflongitudinal growth occurs in the structure as a consequence of thecompression exerted by the riveting, as is known in the riveting art. Toaccommodate this growth, an automated routine in the control systemreleases the clamps 66 serially and then resecures the clamps on theworkpiece.

The carriages 46 shown in FIG. 4 and in greater detail in FIGS. 14 and15, each include a carriage chassis 108 supported vertically by a pairof longitudinally spaced bearing blocks 110 on the rail 44 for rollingmotion therealong, and also for lateral motion relative to the railwhile traversing the bend 22 (as will be discussed below) and also forrotation about a vertical axis, also while traversing the bend 22. Thebearing blocks will be explained in detail in connection With FIGS. 17and 18. The carriage chassis is driven longitudinally along the rail 44by a pair of AC servomotors 112 connected by way of a planetary gearboxand timing belt to drive pinions 113 geared to a gear rack 114 on theside of the bottom track 38. The motor/gearbox assemblies are preloadedby hydraulic cylinders for constant anti-backlash mesh of the drivepinions 133 to the rack 114. The servomotors 112 are arranged in a"leader-follower arrangement in which the lead motor drives its pinionin the driving direction and the other motor biases its pinion in theopposite direction to prevent backlash between the pinions and the gearrack 114.

An Inductosyn faran scale 116 is attached to the bottom track in aprotected position below the gear rack 114 and under a covered housing.A reader engages the faran scale and slides along with the carriage incontact with the faran scale to provide an accurate feedback signal tothe controller as to the longitudinal position of the carriage along therail 44.

Power and communication lines 120 from a power supply and from thecontroller are routed through a communication line trough and are strungon a rolling track system 124 in a well know manner. The bottom of thetrough is provided with a Teflon plate to facilitate the movement of therolling track system in the trough 122.

A tray frame 126 is mounted on vertical guides 128 for vertical motionunder control of a pair of parallel ball screws 130 driven by a motor132 through a right angle divider 134 and two horizontal torque tubes136 to a right angle drive 138 at the head of each ball screw 130. Aresolver 140 coupled to each drive screw follows the helical thread onthe ball screw 130 for vertical motion of, the tray frame, and a faranscale (not shown) on one of the vertical guides 128, in contact with areader mounted on the tray frame, gives feedback information to thecontroller as to the vertical position of the tray frame 126 on thecarriage chassis.

A tray platform 142 is mounted on slides 144 on the tray frame 126 forsliding motion toward and away from the workpiece. An AC servomotor 145,with resolver feedback, is mounted on the tray frame 126 and drives atiming belt to operate a ball screw 146 coupled to the tray platform142. This drive mechanism moves the tray platform toward the wet side ofthe spar to engage an apertured nosepiece 210, connected to the trayplatform 142, with the spar, which interrupts a sensor. Under control ofthe controller, the drive mechanism moves the wet side nosepiece a smallincrement further where it servo-locks in a fixed and unyieldingposition.

An identical AC servomotor arrangement on the dry side carriage movesthe dry side nosepiece 210' into initial clamp-up contact with the sparassembly, until interrupted by sensor contact with the spar. Underprogram control, the drive moves the dry side nosepiece 210 a smallincrement further, then switches from position control to torquecontrol. At a programmed value corresponding to the required clampingforce, the dry side nosepiece 210 is servo locked.

A tool tray 150 is mounted on the tray platform 142 on linear guideways152 extending on a "U-axis" which is in the direction of the X-axis,parallel to the rail 44. The tool tray is a welded steel structure thatmoves in the direction of the U-axis to carry various tools and movethem longitudinally into axially alignment with the axis of thenosepiece aperture for spar assembly operations. U-axis positioning isindependent of positioning on the X, Y, or Z axes.

Movement of the tool tray 150 is by an AC servomotor 154, with resolverfeedback, which is mounted on the tray platform 142. Positioning of thetool tray 150, as well as tools on the tool tray and the carriages 46themselves, is under the control of the system controller, whichreceives data from a data base in which data sets for parts to befabricated can be stored, locates where holes are to be drilled andfasteners inserted in the workpiece, and operates to position thecarriages, tool trays and tools to drill the holes and install thefasteners at the designated places on the workpiece. The servomotor 154drives a ball screw assembly 156 to effect controlled longitudinalsliding movement of the tool tray 150 on the tray platform 142. At fixeddistance positions along the ball screw, flanged nuts make connectionsto various fastening system tool assemblies. The features and details ofthis tool tray motive system are identical on all carriages.

The bearing block 110 shown in FIGS. 17 and 18 includes a bearing base160 in which are mounted four in-line sets of double rollers 162 forsupporting the bearing base 160 on the top surface of the rail 44, andtwo pairs of opposed vertical axis side rollers 164 engaged withopposite sides of said rail 44. A set of wipers 165 surrounds theoutside of the rollers 164 and is in wiping contact with the sides ofthe rail 44 to prevent debris from getting crushed between the rollers164 and the rail 44 and damaging the surface thereof.

A bearing lid 166 sits atop the bearing base 160 and is supportedthereon by a pair or large diameter thrust and radial bearings 168. Thebearing lid is thus able to rotate about a vertical axis on the bearingblock as the bearing block travels linearly along the rail. A pair oflinear recirculating bearing slides 170 and 170' is mounted on the topof both longitudinally spaced sides on the bearing lid 166. The slides170 and 170' are engaged with tracks mounted on the underside of thecarriage chassis 108 for vertical support of the carriage chassis.

A jacking screw assembly 172 is connected between each bearing lid andthe carriage chassis for carriage trimming motion perpendicular to thespar for accommodating the bend in the spar assembly. Trimming maintainsthe axis of the nosepiece and the tooling normal to the spar under alloperating conditions. This function is particularly important duringthose fastening operations that take place in the region of the sparbend 22. During motion in the vicinity on the bend 22, the carriage issimultaneously pushed and pulled by the jacking screw assemblies 172,and this opposing linear motion results in rotation of the carriageabout the Y-axis zero vertical reference sufficient to maintain thenosepiece aperture normal to the spar stack.

An AC servomotor 174 is provided for each bearing block 110, withabsolute resolver feedback, to provide rotating output to a ball screw176 connected in line with the servomotor 174. Each servomotor 174 isconnected by a flange 178 on the motor frame to the carriage structure.A cam follower assembly 180 is incorporated in the position of the ballscrew nut. The top side of the cam follower is connected to the bearinglid 166 so the two trim assemblies provide offsetting output, andvertical axis rotation.

As shown in FIGS. 22-24, the tray platform 142 has a front side facingthe workpiece clamp-up position 67. The front side is formed as a strongsteel casting known as the "headstone" 200. The headstone extends thefull longitudinal length of the tray platform 142 and is slightly curvedin a convex shape as seen from the workpiece clamp-up position, as shownin FIG. 22. The headstone provides clamp-up force on the workpiece andthe shape, size and material of the headstone allows for powerfulclamp-up forces to be exerted by the headstone without significantdeflection.

A rotating nose 202 is mounted in the center of the headstone 200 andprojects forwardly therefrom toward the workpiece clamp-up position. Asshown in FIG. 19, the rotating nose 202 is a cup-shaped member having acylindrical body 204 open at the back end 206 and with an aperturedfront end wall 208. A nosepiece 210 is mounted in a stepped aperture inthe front end wall 208. The nosepiece has a front end nose 212 that issquare in cross-section for maximum compressive strength for a thinwalled structure. The nose bears the full compressive clamp-up force andmust be able to fit into positions closely adjacent to stiffeners andrib posts on the spar where drilling, riveting and other process stepsare to be performed.

The cylindrical body 204 of the rotating nose 202 has an outwardlyprojecting radial flange 214 to which an annular ring gear 216 isattached. A motor 218 with resolver feedback drives a pinion 220 inmeshing engagement with the ring gear 216 to rotate the rotating nose202. A second motor 222, also with a pinion engaged with the ring gear216, biases the ring gear in the opposite direction to eliminate anybacklash in the gear connection with the ring gear 216. A brake 224 isactivated by the control system to automatically grip the ring gear 216when the rotating nose has been rotated to the desired position so thatit does not become accidentally jarred to the wrong angle.

A proximity sensor 226 is attached to the rotating nose 202 at thejunction of the nosepiece 212 and the front end wall 208. The proximitysensor 226 detects when the nosepiece makes contact with the workpiece,as will be explained below.

As shown in FIGS. 22-24, a plurality of tools are mounted side-by-sideon the tool trays 150 for positioning, in proper order, in line with theaxis of the nosepiece 212 by longitudinal movement of the tool tray 15on its linear guideways 152. The tools on the tool trays 150 on both wetand dry side carriages can be moved into and out of engagement with theworkpiece through the bore of the nosepiece 210 after the tray platforms142 on the wet side and dry side carriages have moved into clampingengagement, without unclamping. In this way, all operations necessary toinstall a fastener can be performed without unclamping.

The tools on the dry side tool tray 150 include a bolt inserter anddriver 230, a drill 232, an electromagnetic riveter 234, a reamer 236, acold work tool 238 (shown aligned with the nosepiece 210, and a riverinserter 240. These tools will be described briefly below.

The drill 232 is a horizontally mounted motor-spindle assembly, totallyenclosed and water cooled, powered by a high frequency, AC inductionmotor. It is mounted on a slide on the tool tray 150 for drill feed byan AC servomotor. The drill is capable of variable speed at constanttorque. The drill spindle motor is water cooled utilizing a water coolermounted on the carriage. The front bearing is equipped with a PromessThrust Monitor for sensing when the thrust on the bearing exceeds apredetermined magnitude, indicating that the drill is becoming dull. Asignal is sent, in such event, by the system controller to a monitor tosignal the operator to change the drill bit at the next appropriateopportunity.

The cold work tool is a standard tool provided by Fatigue Technology inSeattle, Wash. Cold working is the process of using mechanical force toexpand the diameter of a drilled hole to create a region of residualcompressive stress for a distance of up to one-half hole diameter fromthe hole edge. This process substantially improves the fatigue life ofthe fastened joint.

A split mandrel is inserted through the drilled hole. The mandrel isexpanded and pulled back through the hole with known interference andforce. Positioning feed of the cold work system is accomplished with aDC-powered linear actuator. The pull force is developed by means of anair-over-oil hydraulic intensifier piston pump mounted on the carriagewith air lines running to the unit. An automatic lubrication applicatorsystem 241 provides lubrication for the split mandrel.

The automatic lubrication system 241 is illustrated in FIGS. 25-28. Itincludes a base 242 having a cylindrical extension tube 244 secured toan upright support plate 246 which is part of the base. The base ismounted on a slide controlled by a servomotor (not shown), like theother tools on the tool tray 150. A fluid line 248 runs from anadjustable metering valve 250 on the back of a lubricant reservoir 252to a fitting communicating with an axial passage 254 in the extensiontube 244. An air line 256 communicates between an air fitting 258 forconnection to a source of air pressure, to a pressure regulator andgauge 260 and thence to the air space over the lubricant reservoir topressurize the reservoir.

A lubricant applicator 261, shown in FIGS. 27 and 28, is mounted on thefront end of the extension tube 244. The applicator includes acylindrical body 262 and a sleeve 264. The body 262 is bolted to the endof the extension tube and has an axial passage 266 in communication withthe axial passage 254 in the extension tube 244. The passage 266 opensto the external surface of the body 262 between two grooves 268 and 270,each having a sealing O-ring. A second section 266' of the axial passage266 communicates between the end 272 of the body 262 and the externalsurface of the body between the groove 270 and an adjacent groove 274,also holding a sealing O-ring.

A groove 276 in the inside surface of the sleeve permits fluid to flowaround the middle sealing O-ring in the groove 270 when the sleeve 264is moved against the biasing force of a compression spring 278 coiledbetween a shoulder 280 and the back end 282 of the sleeve 264. Thismovement occurs when the tip 284 of the applicator is inserted into ahole 285 and the front shoulder 286 of the sleeve 264 engages theworkpiece 288. Continued forward movement of the base 242 along itsslide, driven by its servomotor, pushes the body 262 into the sleeve anactuating distance "X", thereby permitting flow of lubricant through theaxial passages 266 and 266', through a check valve 290, and into aperforated axial tube 292 in the tip 284, and out into a sleeve 294 ofporous wicking material such as felt. The lubricant is uniformlydistributed as shown in FIG. 28 through the wicking sleeve, and theamount of lubricant is controlled by the dwell time of the applicator inthe position shown in FIG. 28. The applicator is retracted automaticallyafter the preset dwell time, thereby automatically shutting off the flowof lubricant to the tip 284.

After a hole 285 has been drilled, cold worked, and reamed, a holechecker 300, shown in FIG. 29, is indexed to the hole and a probe 302 isinserted into the hole by actuation a linear positioning device 304 toadvance the hole checker on its slide 306 on the tool tray 150. Theprobe 302, shown enlarged in FIG. 30, is a stylus-type device slightlylarger than the nominal hole diameter and having two opposingspring-loaded ball contacts 307. Contact with the wall of the hole 285causes the balls to displace inward toward the stylus center, wedgingand displacing the conical-shaped core 308 of a differentialtransformer. The wedging action is translated into linear displacement.The core 308 is both the main interior element of the stylus and alsothe core 308 of a linear variable differential transformer (LVDT) 308.Linear displacement of the core 308 produces an AC voltage outputproportional to the displacement of the transformer core relative to itswindings. A spring (not shown) on the core axis anchors it to the stylusshell, ensuring displacement only when measuring diameters less than thedistance between the ball contacts.

The probe takes two measurements at each of two hole depths, and sendsanalog signals that can be processed to determine if the holecharacteristics are within allowance for riveting or bolting. Proberotation for measurement is accomplished with a pneumatic rotaryactuator main shaft 314 which is supported for rotation on bearings 316.A remote centering compliance device 318 permits the probe 302 to moveparallel to itself to self-center in the hole.

The remote centering compliance device 318 may permit the probe 302 tosag slightly, so a centerlocking actuator 320 can be energized toadvance the shaft 314 into a receptacle 322 in the front end of theremote centering compliance device 318 to lock it up in a rigid axiallyaligned configuration to ensure the probe tip remains on axis. Once thetip is in the hole, the actuator 320 can withdraw the shaft 314 so theprobe can move parallel to itself to lie exactly parallel to the holeaxis to ensure an accurate measurement.

After the hole is checked in two or more planes through the axis of thehole, a fastener may be fed to the hole. An electro-pneumatic fastenerfeed system supplies bolts and rivets from trays on the dry sidecarriages, and nuts and collars from magazines from the wet sidecarriages. Fastener trays and magazines are preloaded with highcompression type fasteners, such as bolts and rivets, and are deliveredloaded to the carriage. Fasteners are selected from the trays (bolts andrivets) or magazines (nuts and collars) under program control andpneumatically fed to insertion positions unique to each tool. Sensorsverify fastener type and position in the tooling prior to initiating thefastening sequence. Fasteners differ in size (diameter and length) andtype (bolts, rivets, nuts, collars).

An element of the fastener feed system is shown in FIGS. 33 and 34. Itincludes a nylon tray 330 in which holes 332 have been drilled.Fasteners 334 are stored individually in the holes 332. The depth of theholes 332 was preselected to correspond to the length of the fastener334 so all the fasteners are flush with the top surface of the tray 330.This helps ensure that any mistakes in loading the trays will be easilydetected because the fastener thickness and length will not match thehole diameter and depth.

A small bleed hole 336 is drilled through the bottom of each hole 332communicating with the bottom of the tray 330. A plurality of small feet338 hold the tray off the surface 339 on which it sits to permit air toflow through the bleed holes 336 when fasteners 334 are sucked out ofthe holes 332.

An X-Y positioning system is provided for positioning a suction head 340over the holes 332. The X-Y positioning system is commercially availableand is similar to the standard plotter. It is commonly used for movinglasers over a surface to be scanned or illuminated in a particularpattern. A vertical translator 342 lifts the suction head off of thetray 330 when the tray is to be replaced, but is not necessary to liftthe suction head 340 when moving over the top of the tray 330 since thefriction is small. When the X-Y positioner has moved the suction head tothe correct position as verified by feedback sensors in the positioningsystem, the suction is turned on by blowing air, delivered through anair supply line 341, through a Vaccon tube 342 which generates suctionby air velocity, thereby sucking a fastener out of the hole 332 andpropelling it through a delivery tube 344.

The fastener is propelled through the delivery tube 344 and delivered toa fastener insertion device 230, shown in FIGS. 23 and 24. The insertiondevice 230 slides forward on its slide and pokes the fastener into thehole. The threaded portion of the fastener is a slightly smallerdiameter than the shank portion, and the threaded portion enters thehole, but the shank portion is slightly larger than the hole and must beforced into the hole. A pneumatic seating hammer behind the fastenerinsertion device 230 can be used to seat the fastener, or theelectromagnetic riveter can be used.

The electromagnetic riveter 346 has an electromagnetic actuator,including a coil, a transducer and a driver. The driver is axiallyaligned with the fastener by moving the tray 150 longitudinally, asdescribed previously, so that when the coil is electrically energized,the transducer is forcably repelled away from the coil and the driver ispropelled against the fastener head to seat the fastener head againstthe workpiece surface. A lateral slide on which the electromagneticactuator is mounted for sliding motion toward and away from theworkpiece position is actuated to position the driver against thefastener head, and a sensor determines the lateral position of thedriver relative to the workpiece surface. The controller now knows howfar the fastener must be driven to seat the fastener head against theworkpiece. By tests, the force to seat the fastener head against theworkpiece, without excessive impact between the fastener head and theworkpiece as to cause damage, at incremental distances from theworkpiece has been determined, and those values have been entered in alook-up table in the controller. The controller matches the distance ofthe fastener head from the workpiece with the corresponding value in thelook-up table to determine how hard the fastener must be hit by thedriver. By tests, it has been determined how far away from the fastenerhead the driver must be to deliver a certain force. The controllercommunicates with the motive device for moving the electromagneticriveter and the sensor to move the electromagnetic actuator away fromthe fastener to its home position, and then back toward the fastener.When the driver reaches the predetermined position, the controllertriggers the power supply of the riveter to fire and propel the driverforward against the fastener to seat the fastener against the workpiecesurface.

A nut feeding device 350 and a collar feeding device 352 are provided onthe wet side carriage tool tray 150'. Both devices are virtuallyidentical, so the nut feeding device will be described. A carrousel 354is provide atop the device 350 for carrying a multiplicity of nuts 355.The carrousel 354 has a rotating head 356 from which depend a pluralityof rods 358 and onto which can be slid a multiplicity of nuts. The rodseach have an upper end 360 fixed in the rotating head 356 by screws 362.The rods each have a free lower end 364 space closely adjacent a slidingsurface 366.

The rotating head 356 is rotated by a shaft 368 projecting on an axis ofrotation from the rotating head and coupled by way of a quick releasecoupling 370 to an indexing drive mechanism 372 for rotating the shaft368 to rotate and drive the carrousel about its axis of rotation. Anopening 374 in the sliding surface 366 at one radial position on thecircular path around which the nuts travel as the carrousel rotatesallows the nuts to drop one at a time into a feed slot 376 where theyare blown by and air jet 378 into a channel 380. The nut channel 380curves downwardly for conveying the nut to a nut loading station 384. Anut transfer arm 386 carries the nut laterally to the adjacent nutrunner and holds the nut in front of the nut runner 390, shown in FIG.37, while the socket 392 on the nut runner engages the nut. The nut thenslides into the socket and the transfer arm retracts to allow the nutrunner to advance forward and present the rotating nut to the bolt.

Obviously, numerous modifications and variations of the describedpreferred embodiment are possible and will occur to those of ordinaryskill in the art in view of this disclosure. Accordingly, it isexpressly to be understood that these other embodiments, and theirequivalents, may be practiced while remaining within the spirit andscope of the invention as defined in the following claims, wherein

We claim:
 1. An automated assembly machine for fabricating largemechanical structures from a multiplicity of individual parts,comprising:a floor assembly jig having a multiplicity of clamps forreceiving and holding said parts in a desired orientation with respectto each other and in a desired position in space, clamped together in aworkpiece clamp-up position, having supports and guides for supportingand guiding a pair of carriages along the length of said machine onopposite sides of said workpiece clamp-up position; a pair of carriagessupported and guided on supports and guides on said floor assembly jig,said carriages being disposed on opposite sides of said workpiececlamp-up position; a first drive mechanism for independently drivingsaid carriages longitudinally along said guides and supports; a seconddrive mechanism for moving said carriages vertically with respect tosaid floor assembly jig; a tool tray mounted on at least one of saidcarriages, said tool tray being mounted on a shifting mechanism forlongitudinal movement on said at least one carriage relative to saidfloor assembly jig; a plurality of tools, including a drill, a holediameter measurement probe, a nut runner, and an electromagneticriveter, mounted on slides on said tool tray for lateral movement towardand away from said workpiece clamp-up position; a motive device formoving each of said tools toward and away from said workpiece clamp-upposition; whereby said tools can be positioned at any desired positionon said workpiece clamp-up position by moving said at least one carriagelongitudinally along said floor assembly jig to a desired longitudinalposition, and raising said at least one carriage to elevate said tooltray to a desired elevation, shifting said tool longitudinally alongsaid at least one carriage to align one of said tools with the desiredposition, and sliding the one of said tools laterally into saidworkpiece clamp-up position.
 2. An automated assembly machine as definedin claim 1, further comprising:a nose on a side of said tool trayadjacent said workpiece clamp-up position, and a translating mechanismfor moving said nose into said workpiece clamp-up position to engage aworkpiece supported therein to clamp said workpiece while said toolsperform their functions.
 3. An automated assembly machine as defined inclaim 1, further comprising a computer control system for controllingthe movement of said carriages, tool tray, and tools, said computercontrol system including:a data base in which data sets for parts to befabricated can be stored; a system controller for positioning saidcarriages, and tool tray and said tools to locate where holes are to bedrilled and fasteners inserted in said workpiece.
 4. An automatedassembly machine as defined in claim 3, further comprising:an automatedroutine in said control system for releasing said clamps serially andthen resecuring said clamps on said workpiece to accommodate growth ofthe length of said workpiece as high compression fasteners are installedin said workpiece.
 5. An automated assembly machine for fabricatinglarge mechanical structures, as defined in claim 1, further comprising afastener feed system for selecting a fastener needed for a particularfastening location from a fastener storage area and delivering thefastener to a workpiece where the fastener is to be installed, saidfastener feed system including:a tray mounted on one of said carriagesand having a floor and a grid partition arrangement defining amultiplicity of vertically elongated, upwardly opening cells for holdingsingle fasteners in a vertical orientation; a delivery tube forconveying fasteners, selected and extracted from said tray, to a devicefor inserting fasteners into the workpiece; a suction head attached tosaid proximal end of said delivery tube for contacting a top edge ofsaid grid partition arrangement and applying suction to a selected cellto suck the fastener in said cell through said suction head and intosaid delivery tube; a motive device for positioning said suction headover said selected cell; and a control system for controlling saidmotive device.
 6. An automated assembly machine for fabricating largemechanical structures, as defined in claim 5, wherein:said tray is ablock of material into which cell holes have been drilled to form saidcells, said grid partition arrangement comprising the material of saidblock between said cell holes.
 7. An automated assembly machine forfabricating large mechanical structures, as defined in claim 6, furthercomprising:an air hole in the bottom of each cell hole and communicatingwith the bottom surface of said tray; whereby air can flow from belowsaid tray up through said air hole and through said cell when saidsuction head sucks said fastener out of said cell.
 8. An automatedassembly machine for fabricating large mechanical structures, as definedin claim 7, further comprising:a plurality of feet on said bottomsurface of said tray to provide an air space between said bottom surfaceand the surface on which said tray sits; whereby air can flow into saidair holes when said suction head sucks said fastener out of said cell.9. An automated assembly machine for fabricating large mechanicalstructures, as defined in claim 6, wherein:said cell holes are eachdrilled to a depth equal to the length of the fastener that is to beplaced in the cell hole, whereby the tops of all of said fasteners insaid tray, when said tray is fully loaded, lie substantially flush withthe top surface of said partitions.
 10. An automated assembly machinefor fabricating large mechanical structures, as defined in claim 5,wherein:said motive device includes a gantry mounted on two slides, oneeach on each of two opposite sides of a tray holder, for movement in an"X" direction, and a slider mounted on said gantry for carrying saidsuction head in a "Y" direction orthogonal to said "X" direction.
 11. Anautomated assembly machine for fabricating large mechanical structures,as defined in claim 5, wherein said control system comprises:a machinereadable code on said tray for identifying each individual tray; areader adjacent to a holder for said trays for reading said code; acomputer having a look-up table in which the location of each fastenersize in each tray is stored; and a communication network forcommunicating to said computer the identification of each tray as readby said reader, and for communicating from said computer to said motivedevice instructions as to the location of the next fastener to beselected from said tray for insertion into said workpiece.
 12. A methodof automatically fabricating large mechanical structures from amultiplicity of individual parts, comprising:receiving and holding saidparts in a desired orientation with respect to each other; clamping saidparts together in a workpiece clamp-up position in their relativeposition with respect to each other which said parts will occupy in saidlarge mechanical structure; supporting and guiding a pair of carriagesalong opposite sides of said workpiece clamp-up position; independentlydriving said carriages longitudinally and vertically with respect tosaid workpiece clamp-up position; supporting a tool tray on a shiftingmechanism on at least one of said carriages for longitudinal movement onsaid at least one carriage relative to said workpiece clamp-up position;and individually mounting a plurality of tools, including a drill, ahole diameter measurement probe, a bolt inserter, a cold working tool,and an electromagnetic riveter on slides on said tool tray for movementlaterally toward and away from said workpiece clamp-up position andperforming drilling and fastening operations on said parts to fastensaid parts together to make said large mechanical structure.
 13. Amethod of automatically fabricating large mechanical structures asdefined in claim 12, further comprising feeding fasteners to a fastenerinstallation device on said tool tray for installation of said fastenersinto holes in a workpiece, said fastener feeding step including:storingsaid fasteners in upwardly opening individual cells defined by cellwalls in trays located in proximity to said installation device; movinga suction head over an individual cell containing a fastener to beinstalled in said workpiece and into contact with the top surface ofsaid cell walls to seal said suction head to said cell walls to minimizeshort-circuiting of air around said cell and into said suction head;sucking said fastener out of said cell and through a delivery tube tosaid installation device.
 14. A method as defined in claim 13, whereinsaid moving step includes:identifying said tray; looking up in acomputer, in a look-up table associated with said tray, the location ofthe next fastener to be delivered to said installation device;communicating to a motive device the location of said next fastener insaid tray; and operating said motive device to carry said suction headto said location of said next fastener in said tray.
 15. A method asdefined in claim 14, wherein said identifying step includes:reading amachine readable code on said tray and communicating said code to saidcomputer.
 16. A method as defined in claim 14, wherein said operatingstep includes:sliding a gantry spanning said tray over said tray to aposition along one edge of said tray corresponding to the position ofthe cell holding said next fastener; and sliding a carrier holding saidsuction head along said gantry to a position along another edge of saidtray, orthogonal to said one edge, to position said suction head exactlyover said cell holding said next fastener.
 17. A method as defined inclaim 14, wherein said identifying step includes:scanning a machinereadable code on said tray to discern the identity of that configurationof tray; and communicating to said computer the identity of said tray toenable said computer to find said associated look-up table.
 18. A methodas defined in claim 13, wherein said suction head moving stepincludes:moving a gantry over said open ends of said cells in said trayto position said gantry over said tray at a desired distance from oneedge of said tray; sliding a carrier on which said suction head ismounted lengthwise along said gantry to position said suction head at adesired distance from an orthogonal edge of said tray and over a desiredcell.
 19. A method as defined in claim 18, further comprising:extendingsaid suction head downward into contact with said tray and applyingsuction to said suction head to effect said suction step.
 20. A methodof automatically fabricating large mechanical structures from amultiplicity of individual parts, comprising:receiving and holding saidparts in a desired orientation with respect to each other; clamping saidparts together in a workpiece clamp-up position in their relativeposition with respect to each other which said parts will occupy in saidlarge mechanical structure; supporting and guiding a pair of carriagesalong opposite sides of said workpiece clamp-up position; supporting atool tray on a shifting mechanism on at least one of said carriages forlongitudinal movement on said at least one carriage relative to saidworkpiece clamp-up position; individually moving a plurality of tools,including a drill, and a fastener insertion device, on slides on saidtool tray laterally toward and away from said workpiece clamp-upposition to perform operations on said parts to fasten said partstogether to make said large mechanical structure; drilling a hole insaid workpiece with said drill; feeding a fastener to said fastenerinsertion device; inserting a distal end of said fastener, opposite aheaded end thereof, into said hole so that said distal end is tightlywedged into said hole and said headed end of said fastener is spacedfrom said workpiece surface; extending a driver of an impulse actuatorinto contact with said fastener head; and actuating said impulseactuator to seat said fastener against said workpiece surface.
 21. Amethod of automatically fabricating large mechanical structures asdefined in claim 20, further comprising:sensing and recording theposition of said driver when it is in contact with said fastener head todetermine how far said fastener must be driven into said hole to seatsaid fastener head against said workpiece surface; actuating saidimpulse actuator to produce sufficient energy to drive said fastenerinto said hole to seat said fastener head against said workpiece, butwith less energy than would cause said fastener head to damage saidworkpiece.
 22. A method of seating a fastener as defined in claim 21,wherein:said sensing step includes moving a slider of an LVDT,operatively connected to said driver, with said driver and measuring thevoltage of the signal from said LVDT to ascertain the position of saiddriver.
 23. An automated assembly machine for fabricating largemechanical structures from a plurality of components, comprising:a floorassembly jig for supporting said components of said structure in correctposition relative to one another while said structure is being fastenedtogether; at least one pair of carriages supported on said floorassembly jig for carrying tools for fastening said structure together; atool tray mounted on at least one of said carriages, said tool traybeing mounted on a shifting mechanism for longitudinal movement on saidat least one carriage relative to said floor assembly jig; a pluralityof tools, including a drill, a rivet inserter, and an electromagneticriveter, mounted on slides on said tool tray for lateral movement towardand away from said workpiece clamp-up position; a fastener feed systemfor selecting a fastener needed for a particular fastening location froma fastener storage area on at least one of said carriages, and fordelivering the fastener to said rivet inserter for installation of arivet in a hole drilled by said drill, said fastener feed systemincluding:a tray having a multiplicity of vertically elongated, upwardlyopening cells for holding single fasteners in a vertical orientation; adelivery tube for conveying fasteners, selected and extracted from saidtray, to a device for inserting fasteners into the workpiece; a suctionhead attached to said delivery tube for applying suction to a selectedcell to suck the fastener in said cell through said suction head andinto said delivery tube; a motive device for positioning said suctionhead over said selected cell; and a control system for controlling saidmotive device.
 24. An automatic fastening system for assembling largemechanical structures, comprising:a floor assembly jig for supportingsaid components of said structure in correct position relative to oneanother while said structure is being fastened together; a pair ofcarriages supported on said floor assembly jig for carrying tools forfastening said structure together; a fastener feed system for selectinga fastener needed for a particular fastening location from a fastenerstorage area on at least one of said carriages and delivering thefastener to a workpiece where the fastener is to be installed, saidfastener feed system including:a tray having a multiplicity ofvertically elongated, upwardly opening cells for holding singlefasteners in a vertical orientation; a delivery tube for conveyingfasteners, selected and extracted from said tray, to a device forinserting fasteners into the workpiece; a suction head attached to saiddelivery tube for applying suction to a selected cell to suck thefastener in said cell through said suction head and into said deliverytube; a motive device for positioning said suction head over saidselected cell; and a control system for controlling said motive device.